Fortunately, most of the most prominent living moral & political philosophers have such pages, although some who would surely be on the list do not (e.g., Allan Gibbard, Thomas Nagel, Martha Nussbaum). I only count those most of whose citations are in moral and political philosophy. (I excluded those primarily working in bioethics, which has promiscuous citation practices, as does medicine as a scholarly field generally.)

1. Will Kymlicka (Queen’s U [Canada]): 100,520
2. Peter Singer (Princeton [emeritus]): 90,430
3. Phillip Pettit (Princeton/ANU): 51,890
4. Robert Goodin (ANU): 43,950
5. Thomas Pogge (Yale): 43,830
6. Joshua Cohen (Apple/Berkeley): 41,100
7. David Miller (Oxford [emeritus]): 40,500
8. John Broome (Oxford [emeritus]): 35,100
9. Allen Buchanan (Arizona/Duke [emeritus]): 28,600
10. Elizabeth Anderson (Michigan): 25,880
11. T.M. Scanlon (Harvard): 25,630
12. Christine Korsgaard (Harvard): 24,750
13. Philippe van Parijs (Louvain [emeritus]): 21,350
14. Ingrid Roybens (Utrecht): 20,830
15. Stephen Darwall (Yale): 15,660
16. Walter Sinnott-Armstrong (Duke): 15,300
17. Michael Smith (Princeton [emeritus]): 14,130
18. David Velleman (Johns Hopkins; NYU [emeritus]): 13,680
19. Jeff McMahan (Oxford [emeritus]): 13,270
20. Gerald Dworkin (UC Davis [emeritus]): 12,880

The top of the list is dominated by philosophers who work in political philosophy, no doubt because that work gets cited more outside academic philosophy (e.g., in political science and law journals). The “most cited” “pure” moral philosopher on the list is Korsgaard.